Being well known in the art, a recording disc player such as a digital audio disc player includes pick-up means which is positioned in the proximity of a recording surface of a recording disc being rotated at a certain speed on a turn-table. The pick-up means produces an electric signal containing therein a track signal previously recorded on the recording surface in the form of one or more annular or spiral, i.e. circumferentially extending tracks. The pick-up means produces a detecting point on the surface of the disc which point is to be aligned on to a target track from which the track signal is detected or read. Since the so-called tracking servo of the pick-up means directs the detecting point onto the target track by a tracking servo system which, in turn, is operative on the basis of an error signal representing amount and direction of deviation of the pick-up point from the target track, the pick-up point must be located within a recorded region which is defined between radially innermost and outermost tracks on the recording surface. It is to be understood that the tracking servo system does not operate when the pick-up point is located within a non-recorded region due to lack of usable electric signal from the pick-up means.
Since, however, the area or position of the recorded region on the recording surface of a recording disc is usually not definite or previously unknown, that is, different from disc to disc, the detecting point of the pick-up means in a recording disc player is subject to move or dislocate from the recorded region and enter the non-recorded region, with the result that the tracking servo system becomes inoperative due to lack of the electric signal from the pick-up means. The system is, therefore, required to quickly detect the removal or dislocation of the pick-up point from the recorded region during the pick-up operation and to return the pick-up point back to the recorded region.